The present invention relates to a printhead, a printing apparatus using the printhead, a printhead cartridge, and a printing element substrate and, more particularly, to a printhead employing an ink-jet scheme of discharging ink by utilizing, e.g., heat energy, a printing apparatus using the printhead, a printhead cartridge, and a printing element substrate.
In a printhead employing an ink-jet scheme of printing by utilizing heat energy, heat-generating elements are formed at a portion which communicates with discharge orifices for discharging ink droplets. Power is supplied to the heat-generating elements for only about several microseconds to generate bubbles in the ink. The ink droplets are discharged from the discharge orifices by utilizing the bubbling power, thereby printing. In this printhead, a large number of discharge orifices and heat-generating elements can be arranged at a high density. Thus, high-quality image printing can be performed.
When all the heat-generating elements of the printhead are driven simultaneously, the total current instantaneously supplied to the printhead becomes undesirably large. Usually, several ten to several hundred heat-generating elements are divided into a plurality of blocks. The driving timings of the respective blocks are slightly differed from each other, so all the heat-generating elements of the printhead are controlled not to be driven simultaneously. In this manner, the total current which flows instantaneously is suppressed low.
To drive a large number of heat-generating elements, a driving circuit for the elements is incorporated in the printhead, such that the number of wires between the printhead and a printing apparatus on which the printhead is mounted does not increase. In a widely used structure, this driving circuit is incorporated in a Si (silicon) wafer used as a substrate for the heat-generating elements.
The arrangement of the driving circuit varies, and its typical arrangement will be described below.
The driving operation of each heat-generating element is controlled by a block control signal (BLKn) representing the block number of the corresponding heat-generating element and a print signal (DATA) corresponding to the block control signal As the block control signal (BLKn), one obtained by encoding the block number into binary data is used. A value obtained by dividing the number (T) of all the heat-generating elements by a total number (N) of blocks is the number of heat-generating elements (M=T/N) that can be driven simultaneously by one driving operation. If 1 bit of print data corresponds to one heat-generating element and the print data is transferred in a number of bits corresponding to the number of heat-generating elements which are to be driven simultaneously by one driving operation, M corresponds to the number of bits of the print signal (DATA) that drives the print elements simultaneously by one driving operation.
The driving circuit has gates and transistors corresponding in number of bits to the number (T) of heat-generating elements. The driving circuit also has shift registers and latch circuits corresponding in number to the number of bits of the print signal (DATA) which drives the print elements simultaneously by one driving operation and to the number of bits of the block control signal (BLKn). One serial data formed of such a print signal (DATA) and block control signal (BLKn) is serially transferred from the printing apparatus to the shift registers and latched. The latched block control signal is decoded. Consequently, transistors corresponding to the respective heat-generating elements are driven through gates corresponding to the driving signals supplied to the respective blocks.
The transistors can be either bipolar transistors or FETs.
The above conventional driving circuit has the following problems.
If the printhead has many heat-generating elements, the bit length of the serial data formed of the print signal and block control signal increases. Serial data transfer is performed by using one signal line.
Assume that an increase in cost of the manufacture of the printhead is to be prevented by introducing a semiconductor manufacturing apparatus and producing circuit substrates for the printheads on a mass production basis, and that the cost is to be reduced by commonizing devices. In order to practice such cost increase prevention and cost down, if the same semiconductor process is used for manufacturing the printheads, manufacture cannot be performed by forming a circuit in which the transfer clock frequency of serial data is specially increased.
Therefore, as the bit length of the serial data increases, the time required for transferring the serial data increases naturally. As a result, the transfer time becomes an obstacle in shortening the print time.
The present invention has been made in view of the above prior art, and has as its object to provide a printhead which can print at a higher speed even if the number of print elements is large, a printing apparatus using the printhead, a printhead cartridge, and a printing element substrate.
In order to achieve the above object, a printhead according to the present invention has the following arrangement.
More specifically, the printhead comprises Mxc3x97N printing elements divided into N blocks each consisting of M printing elements, and time-divisionally driven with M printing elements for each of N times, Mxc3x97N driving circuits for driving the Mxc3x97N driving elements by supplying power thereto, a first shift register for inputting print signals corresponding to, of print signals corresponding to the M printing elements, L (L less than M) printing elements serially from a first signal line by using a clock signal, and for temporarily storing the input print signals, a second shift register for inputting print signals corresponding to, of the print signals corresponding to the M printing elements, (Mxe2x88x92L) printing elements and a select control signal for selecting one of the N blocks serially from a second signal line by using the clock signal, and for temporarily storing the input print signals and the select control signal, and a selective driving circuit for driving the M printing elements belonging to a block selected on the basis of the select control signal, by the print signals which are stored in the first and second shift registers and correspond to the M printing elements.
The printhead may comprise a first latch circuit for latching the print signals stored in the first shift register and corresponding to the L printing elements, a second latch circuit for latching the print signals stored in the second shift registers and corresponding to the (Mxe2x88x92L) printing elements, and a third latch circuit for latching the select control signal stored in the second shift register.
The printhead may comprise a decoding circuit for decoding the select control signal latched by the third latch circuit, thus forming a block select signal for performing block selection.
The selective driving circuit may include an AND circuit for calculating logical products of the print signals latched by the first and second latch circuits and the block select signal, and may select printing elements to drive on the basis of a calculation result of the AND circuit.
In place of providing a decoding circuit, the block select control signal latched by the third latch circuit may be a block select signal which does not need decoding.
The first, second, and third latch circuits preferably perform latch operation in response to a common latch signal.
The Mxc3x97N printing elements preferably include electrothermal transducers, and the printhead preferably includes an ink-jet printhead for printing by discharging ink. This ink-jet printhead further preferably generates heat energy to be supplied to the ink by supplying power to the electrothermal transducers, so the ink is discharged by utilizing the heat energy.
According to another aspect of the present invention, there is provided a printhead cartridge comprises a printhead and an ink tank for holding ink to be supplied to the printhead being connected to each other, the printhead comprising Mxc3x97N printing elements,
Mxc3x97N driving circuits for dividing the Mxc3x97N driving elements into N blocks each consisting of M printing elements and time-divisionally driving M printing elements N times each, a first shift register for inputting print signals corresponding to, of print signals corresponding to the M printing elements, L (L less than M) printing elements serially from a first signal line by using a clock signal, and for temporarily storing the input print signals, a second shift register for inputting print signals corresponding to, of the print signals corresponding to the M printing elements, (Mxe2x88x92L) printing elements and a select control signal for selecting one of the N blocks serially from a second signal line by using the clock signal, and for temporarily storing the input print signals and the select control signal, and a selective driving circuit for driving the M printing elements belonging to a block selected on the basis of the select control signal, by the print signals which are stored in the first and second shift registers and correspond to the M printing elements.
The printhead and the ink tank can be separated from each other, or can be integral with each other.
According to still another aspect of the present invention, there is provided a printing apparatus for printing comprises a printhead and control means for controlling so as to convert print data into print signals corresponding to M printing elements per block printing, and to transfer the print signals to the printhead through the first and second signal lines by using a clock signal, the printhead comprising Mxc3x97N printing elements, Mxc3x97N driving circuits for dividing the Mxc3x97N driving elements into N blocks each consisting of M printing elements and time-divisionally driving M printing elements N times each, a first shift register for inputting print signals corresponding to, of print signals corresponding to the M printing elements, L (L less than M) printing elements serially from the first signal line by using the clock signal, and for temporarily storing the input print signals, a second shift register for inputting print signals corresponding to, of the print signals corresponding to the M printing elements, (Mxe2x88x92L) printing elements and a select control signal for selecting one of the N blocks serially from the second signal line by using the clock signal, and for temporarily storing the input print signals and the select control signal, and a selective driving circuit for driving the M printing elements belonging to a block selected on the basis of the select control signal, by the print signals which are stored in the first and second shift registers and correspond to the M printing elements.
The control means preferably controls to transfer an enable signal, in order that while transferring the print signals corresponding to one block printing to the printhead, printing elements corresponding to one block for which transfer has been performed immediately before this transfer are driven, thereby printing.
According to still another aspect of the present invention, there is provided a printing element substrate comprises at least M printing elementsxc3x97N blocks and Mxc3x97N driving circuits corresponding to the M printing elementsxc3x97N blocks, a first shift register for inputting print signals corresponding to, of print signals corresponding to the M printing elements, L (L less than M) printing elements serially from a first signal line by using a clock signal, and for temporarily storing the input print signals, a second shift register for inputting print signals corresponding to, of the print signals corresponding to the M printing elements, (Mxe2x88x92L) printing elements and a select control signal for selecting one of the N blocks serially from a second signal line by using the clock signal, and for temporarily storing the input print signals and the select control signal, and a selective driving circuit for driving the M printing elements belonging to a block selected on the basis of the select control signal, by the print signals which are stored in the first and second shift registers and correspond to the M printing elements, wherein the at least M printing elementsxc3x97N blocks, the Mxc3x97N driving circuits, the first shift register,the second shift register and the selective driving circuit are formed on one substrate.
With the above arrangement, according to the present invention, print signals necessary for driving the M printing elements belonging to each of the N divisional blocks and the select control signal necessary for block selection are transferred by inputting the print signals corresponding to the L (L less than M) printing elements serially from the first signal line by using the clock signal and inputting the print signals corresponding to the remaining (Mxe2x88x92L) printing elements and the corresponding select control signal serially from the second signal line by using the same clock signals.
According to still another aspect of the present invention, there is provided a printhead comprises a plurality of printing elements, dividing/driving circuits for dividing the plurality of printing elements into a plurality of blocks and driving the plurality of blocks, a first shift register for inputting print signals corresponding to, of print signals corresponding to a plurality of printing elements constituting one block, a predetermined number of printing elements serially from a first signal line by using a clock signal, and for temporarily storing the input print signals, a second shift register for inputting print signals corresponding to printing elements different from the predetermined number of printing elements constituting the one block and a block select signal for selecting a block to be driven serially from a second signal line by using the clock signal, and for temporarily storing the input print signals and the block select signal, and a driving circuit for driving printing elements on the basis of the print signals stored in the first and second shift registers and the block select signal stored in the second shift register.
According to still another aspect of the present invention, there is provided a printing element substrate comprises a plurality of printing elements, dividing/driving circuits for dividing the plurality of printing elements into a plurality of blocks and driving the plurality of blocks, a first shift register for inputting print signals corresponding to, of print signals corresponding to a plurality of printing elements constituting one block, a predetermined number of printing elements serially from a first signal line by using a clock signal, and for temporarily storing the input print signals, a second shift register for inputting print signals corresponding to printing elements different from the predetermined number of printing elements constituting the one block and a block select signal for selecting a block to be driven serially from a second signal line by using the clock signal, and for temporarily storing the input print signals and the block select signal, and a driving circuit for driving printing elements on the basis of the print signals stored in the first and second shift registers and the block select signal stored in the second shift register, wherein the plurality of printing elements, the dividing/driving circuits, the first shift register, the second shift register and the driving circuit are formed on one substrate.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.